Microbially Influenced Corrosion of Stainless Steels in Aerobic Aqueous Environments
It is generally observed that the susceptibility to localized corrosion of stainless steels in natural seawater is higher than that of stainless steels in synthetic seawater. The higher susceptibility to corrosion in natural seawater is considered to be caused by microorganisms in the biofilm, and therefore it is attributed to MIC (Microbially Influenced Corrosion). MIC of stainless steels in some plant failure cases in fresh water environments were often observed at welded joints, therefore, it is also important to understand the MIC mechanism for welds of stainless steels.
The contents of this article are as follows ;
(1) Corrosion potential ennoblement in natural seawater : It is considered that the corrosion potential ennoblement in natural seawater is caused by the peroxide generated by the metabolism of aerobic bacteria in the biofilm.
(2) Reproduction of corrosion potential ennoblement by laboratory method : The corrosion potential ennoblement can be reproduced in synthetic seawater by the addition of GOD (Glucose Oxidase) with glucose, due to the peroxide generated by the GOD catalytic reaction.
(3) Effect of the bacterial adhesion on MIC occurrence at welded joint : Bacterial adhesion corresponded with the occurrence of pitting corrosion in weldmetal, therefore, the weld bead shape considered to have significant influence on bacterial adhesion and MIC occurrence in stainless steel.